Abstract
Mycobacterium tuberculosis complex owe their ability to cause infection because of their intracellular survival ability in professional phagocytic cells of human and the ability to enter into stage of dormancy. The aim of this study was to develop an infection model that could be used to study M. tuberculosis and macrophage interactions at molecular level. Four infection models were examined namely opsonised M. bovis BCG / J774.2 macrophage cell line, non-opsonised M. bovis BCG / J774.2 macrophage cell line, opsonised M. tuberculosis / J774.2 macrophage cell line, and non-opsonised M. tuberculosis / J774.2 macrophage cell line infection models. A J774.2 macrophage cell line was synchronously infected with M. bovis (BCG strain) and M. tuberculosis (H37Rv), respectively at different multiplicity of infections (M.O.I). For opsonisation, the organisms were pre-incubated with human serum prior to infection. The infected cell lines were examined by light microscopy and electron microscopy with viable bacterial counts. Macrophage viability was assessed by trypan blue exclusion staining. The results showed higher significant level of infection of J774.2 macrophage cell line by opsonised M. bovis BCG (30 – 40%) compared to non-opsonised M. bovis BCG (<0.1%) at an M.O.I of 50 (p < 0.05) with high macrophage viability. In contrast, there was no significant statistical difference (p > 0.05) in high infectivity (30 - 42%) with high macrophage viability achieved with using non-opsonised M. tuberculosis and opsonised M. tuberculosis, respectively, at an M.O.I of 10. In conclusion, opsonisation is not required for M. tuberculosis / J774.2 infection model in contrast to M. bovis BCG / J774.2 infection model where opsonisation is necessary to achieve high level of infection.
Keywords: Infection, intracellular, mycobac- terium tuberculosis, macrophage
Résumé
Le but de cette étude était de développer un modèle d’infection qui pourrait être utilisée pour étudier le M tuberculose et les interactions des macrophages au niveau moléculaire. Quatre modèles infections étaient examinés : cellules opsonisees et non-opsonisees M.Bovis BCG/J774.2 ; Cellules macrophages opsonisees et non-opsonisees J774.2 synchronisées par différent infections de multiplication. Pour l’opsonisation les organismes étaient pré-incubes dans les sérum humain avant l’infection. Les cellules infectées étaient examinées a l’aide de microscope a lumière et a électron. L’habilite des macrophages était évalué par la teinture de Trypan bleue. Les résultants démontraient un niveau élevé d infection des macrophages du J774.2 par l ;’opsonisation de M.bovis BCG (30-40%) comparée aux moins opsonisees M bovis BCG(<0.1%) a M.O.I de 50 (p<0.05) avec des macrophages plus habiles. Au contraire, il n’y avait pas de différence significative(P>0.05) a l’injectivité plus élevée (30-42%) avec des macrophages plus habiles sans opsonisation des M. tuberculose. a M.O.I de 10. En conclusion, l’opsonisation n’est pas nécessaire pour le M. tuberculose/J774.2 modèle d’infection comparée a M.Bovis BCG/J774.2 modèle d’infection ou l’opsonisation est nécessaire pour achever un niveau d’infection plus élevée.
Correspondence: Dr. O.A.T. Alli, Department of Biomedical Sciences, College of Health Sciences, Ladoke Akintola University of Technology, Osogbo, Nigeria. E-mail: alliot@hotmail.com
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